Abstract: In a supporting electrolyte containing 3.5·10^-5Mpyrocatechol, 0.015 NH₄Ac and at pH 4.7, an adsorptive complex wave of aluminium-pyrocatechol was obtained by single-sweep polarography. The peak potential of the polarographic wave was -0.85V (vs, SCE). The linear relationship between wave height and concentration of Al⁺³ held in the range of 1 ·10^-6- 1. 2·10^-5M.The composition of the complex in the ratio 1:1 was determined. This wave was proved to be an adsorptive wave by several experiments. The mechanism of the electrode reaction was discussed.